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  • 1.
    Duan, Ran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Westerlind, Bo
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Anugwom, Ikenna
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University; Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Virtanen, Pasi
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University.
    Mikkola, Jyri-Pekka
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University; Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Fibre stress-strain response of high temperature chemi-thermomechanical pulp treated with switchable ionic liquids2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 8570-8588Article in journal (Refereed)
    Abstract [en]

    The removal of lignin from a high-temperature chemi-thermomechanical pulp (HT-CTMP) using a switchable ionic liquid prepared from an organic superbase (1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)), monoethanol amine (MEA), and SO2 was investigated. The objective was to measure the fibre properties before and after removal of the lignin to analyse the contributions from lignin in the HT-CTMP fibre to the tensile properties. It was found that the fibre displacement at break - measured in zero span, which is related to fibre strain at break - was not influenced by the lignin removal in this ionic liquid system when tested dry. There was a small increase in displacement at break and a reduction in tensile strength at zero span when tested after rewetting. At short span, the displacement at break decreased slightly when lignin was removed, while tensile strength was almost unaffected when tested dry. Under rewetted conditions, the displacement at break increased and tensile strength decreased after lignin removal. Nevertheless, no dramatic differences in the pulp properties could be observed. Under the experimental conditions, treatment with the ionic liquid reduced the lignin content from 37.4 to 15.5 wt%.

  • 2.
    Halvarsson, Sören
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Wheat straw as raw material for manufacture of medium density fiberboard (MDF)2010In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 5, no 2, p. 1215-1231Article in journal (Refereed)
    Abstract [en]

    Wheat straw was used to produce medium-density fiberboard (MDF). The chemical and physical characteristics of fractionated size-reduced wheat straw were investigated. The pH, pH-buffering capacity, ash, and silicon content increased as wheat straw particle size decreased. Ash of the finest straw, <0.2 mm, had high ash (15%) and silicon (18%) contents. The outer and inner parts of size-reduced straw were analyzed using scanning electron microscopy (SEM). The SEM micrographs revealed a complex ultrastructure containing a notable portion of thin-walled cells approximately 1 mu m thick. Pressurized defibration of size-reduced wheat straw produced lignocellulosic fibers nearly 1.0 mm long combined with approximately 24% of small particles and dust. The high water uptake of straw-based MDF was significantly reduced using melamine-modified urea-formaldehyde (UF) resin and removing wheat straw particles and dust by screening. UF resin was added at levels of 12.5%, 13.1%, and 14%. In terms of water resistance, 12-mm-thick straw MDF displayed thickness swelling below 10%, acceptable according to the EN 622-5 MDF standards. It was concluded that manufacturing wheat straw MDF entails straw size reduction (hammer-milling), removing small particles and dust, and adding melamine-modified UF resin to attain necessary MDF quality standards.

  • 3.
    Lindman, Björn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Lund Univ, Ctr Chem & Chem Engn, Dept Chem, Div Phys Chem, SE-22100 Lund, Sweden.
    Medronho, Bruno
    Univ Algarve, Fac Sci & Technol, P-8005139 Faro, Portugal..
    The Subtleties of Dissolution and Regeneration of Cellulose: Breaking and Making Hydrogen Bonds2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 3, p. 3811-3814Article in journal (Other academic)
    Abstract [en]

    Cellulose dissolution and regeneration are old topics that have recently gained renewed attention. This is reflected in both applications - earlier and novel - and in scientific controversies. There is a current discussion in the literature on the balance between hydrogen bonding and hydrophobic interactions in controlling the solution behavior of cellulose. Some of the key ideas are recalled.

  • 4.
    Moser, Carl
    et al.
    KTH Royal Institute of Technology; Valmet AB.
    Henriksson, Gunnar
    KTH Royal Institute of Technology.
    Lindström, Mikael E.
    KTH Royal Institute of Technology.
    Specific Surface Area Increase during Cellulose Nanofiber Manufacturing Related to Energy Input2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 3, p. 7124-7132Article in journal (Refereed)
    Abstract [en]

    Softwood fibers pretreated with a monocomponent endoglucanase wereused to prepare a series of cellulose nanofiber qualities using amicrofluidizer and 2 to 34 MWh ton-1 of energy input. The specific surfacearea was determined for the series using critical point drying and gasadsorption. Although the specific surface area reached a maximum of 430m2 g-1 at 11 MWh ton-1, the nanofiber yield and transmittance continued toincrease beyond this point, indicating that more energy is required toovercome possible friction caused by an interwoven nanofiber networkunrelated to the specific surface area. A new method for estimating thesurface area was investigated using xyloglucan adsorption in pure water.With this method it was possible to follow the disintegration past the pointof maximum specific surface area. The technical significance of thesefindings is discussed.

  • 5.
    Moser, Carl
    et al.
    KTH.
    Lindström, Mikael E.
    KTH.
    Henriksson, Gunnar
    KTH.
    Toward Industrially Feasible Methods for Following the Process of Manufacturing Cellulose Nanofibers2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 2, p. 2360-2375Article in journal (Refereed)
    Abstract [en]

    Nanocellulose is a recently developed form of cellulose that has the potential to be used in many different industries, ranging from food to high-performance applications. This material is commercially manufactured through the homogenization of chemical pulps, but the process is energy-consuming and is still an important subject for development. Simple, robust methods are required for the quality control and optimization of industrial nanocellulose production. In this study, a number of different methods, based on different principles of monitoring the manufacture of cellulose nanofibers were evaluated and compared for five different nanocellulose qualities, both for their resolution and robustness/ease. Methods based on microscopy, light scattering, centrifugation, and viscosity were examined and all appeared useful for observing the manufacturing process during its initial stage. However, only methods based on centrifugation, turbidity, and transmittance yielded reliable data for the entire manufacturing process. Of these methods, transmittance measurement may be the best candidate for routine use because the method is simple, rapid, and only requires spectrophotometer equipment.

  • 6.
    Paulsson, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Parkås, Jim
    Sodra Innovat, Sodra Cell Varo, SE-43024 Varobacka, Sweden.
    Review: Light-Induced Yellowing Of Lignocellulosic Pulps - Mechanisms And Preventive Methods2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 4, p. 5995-6040Article, review/survey (Refereed)
    Abstract [en]

    This review will focus on recent progress regarding the mechanisms of light-induced discoloration of mechanical and chemimechanical pulps and on the proposed preventive treatments. It is evident that the mechanisms behind photoyellowing of lignin-rich pulps are complex and that several types of reaction pathways may coexist. Photoyellowing proceeds via one initial fast phase and a slower following phase. The fast phase has been ascribed to oxidation of free phenolic groups and/or hydroquinones and catechols to photoproducts of mainly quinonoid character. A multitude of reactions involving several lignin subunits are possible. Important intermediates are phenoxyl radicals, and to some extent ketyl radicals. The importance of the phenacyl aryl ether pathway might be more important than previously thought, even though the original content of such groups is low in lignin. Even though many preventive methods against photoyellowing have been suggested, no cost-efficient treatment is available to hinder photoreversion of lignin-containing paper permanently. Suggested methods for stabilization include chemical modification (etherification and esterification), coating the paper product, addition of radical scavengers, excited state quenchers, or ultraviolet absorbing compounds.

  • 7.
    Sandberg, Christer
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper AB, Norrköping.
    Berg, Jan-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Low Consistency Refining Combined with Screen Fractionation: Reduction of Mechanical Pulping Process Complexity2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 1, p. 882-894Article in journal (Refereed)
    Abstract [en]

    Process intensification is a process development methodology aimed at a considerable reduction in the energy consumption and process complexity. The approach has been applied to mechanical pulping process design. A process denoted as HC-LC-S consisting of single stage high consistency (HC) refining, followed by low consistency (LC) refining and screening was evaluated in mill trials at the Holmen Paper Braviken Mill in Sweden. After LC refining, the pulp was screened, and the reject fraction was fed back to LC refining. Two HC primary refiner types were evaluated, namely single disc (SD) and double disc (DD). Double disc chip refining was more suitable than SD refining for the HC-LC-S process because of the higher light scattering and lower shives content of the final pulp. The tensile index and shives content of the pulp produced with the DD-LC-S process was similar to that of the reference process, consisting of single stage DD refining and HC reject refining, but the fibre length and light scattering were somewhat lower. The specific refining energy was approximately 200 kWh/adt lower for the DD-LC-S process compared with the reference. Additionally, the auxiliary specific energy was 100 kWh/adt lower for the HC-LC-S processes, since a number of equipment units were omitted.

  • 8.
    Yang, Jiayi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Zasadowski, Dariusz
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Biorefining of Spruce TMP Process Water: Selective Fractionation of Lipophilic Extractives with Induced Air Flotation and Surface Active Additive2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 2, p. 4124-4135Article in journal (Refereed)
    Abstract [en]

    Lignocellulose biomass plays an important role in reducing thedependency on fossil fuels and ameliorating the dire consequences ofclimate change. It is therefore important that all the components oflignocellulose biomass are exploited. These components includehemicelluloses and extractives that are liberated and sterically stabilizedduring the thermomechanical pulping and that form the dissolved andcolloidal substance (DCS) in the process water. Biorefining of this processwater can extract these substances, which have a number of promisingapplications and can contribute to the full exploitation of lignocellulosebiomass. This paper presents a simple treatment of unbleached Norwayspruce (Picea abies) process water from TMP (thermomechanical pulping)production using induced air flotation (IAF) and cationic surfactant,dodecyl trimethylammonium chloride (DoTAC) to refine the extractivesand prepare the waters so that hemicellulose could be easily harvested ata later stage. By applying 80 ppm of DoTAC at a pH of 3.5 and 50 °Cbefore induced air flotation, 94% of the lipophilic extractives wererecovered from process water. Dissolved hemicellulose polysaccharideswere cleansed and left in the treated process water. The process enabledefficient biorefining of lipophilic extractives and purification of the processwater to enable more selective harvesting of hemicelluloses in subsequentsteps.

  • 9.
    Zasadowski, Dariusz
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Removal of lipophilic extractives and manganese ions from spruce TMP waters in a customized flotation cell2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 2, p. 2376-2392Article in journal (Refereed)
    Abstract [en]

    The influence of a chelating surfactant, different foaming agents, cationic polyelectrolytes, pH value, and temperature on the purification efficiency of process waters from a mechanical pulp mill has been studied by flotation in a 1 L customized unit. Turbidity measurements and gas chromatography (GC) were carried out to determine the removal and characteristics of dissolved and colloidal substances (DisCo). The manganese ion content in the process waters before flotation and the metal chelate removal capacity by flotation were determined by Inductively Coupled Plasma (ICP) and Atomic Absorption Spectrometry (AAS) measurements. It was found that a 99% removal of complex bound manganese ions and a 94% decrease in turbidity of the TMP water produced at the laboratory can be achieved in a single-stage flotation with a chelating surfactant and a foaming agent. Furthermore, a 91% decrease in turbidity, the removal of up to 96% of resin and fatty acids, and 93% of triglycerides from TMP water can be obtained after application of a foaming agent.

  • 10.
    Zasadowski, Dariusz
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Use of a Voith flotation cell for removal of lipophilic extractives and Mn ions from spruce thermomechanical pulping process waters2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 3, p. 2784-2126Article in journal (Refereed)
    Abstract [en]

    The effects of a chelating surfactant and different foaming agents on the efficiency of cleaning process waters from a thermomechanical pulp (TMP) mill were studied in a Voith flotation cell. Turbidity measurements and gas chromatography were used to determine the removal extent and characteristics of dissolved and colloidal substances (DisCo). The metal ion content in the process waters before flotation and the metal chelate removal after flotation were determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). FiberLab (TM) equipment was used to characterize changes in the size of fibers present in the process waters. The results indicate that a decrease in turbidity of up to 91% and the removal of 80% of lipophilic extractives in the TMP water could be obtained using a single-stage flotation unit. Furthermore, the foam fraction was within 5% of the initial volume, and 100% of the Mn2+/chelating surfactant complex added to the TMP water was removed.

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